From Static Biomimetics to Programmable and Adaptive Systems: Advances in Milli-structures in Directed Fluid Transport

Abstract Directed fluid transport is critical to diverse applications spanning water purification, atmospheric water harvesting, point-of-care diagnostics, thermal management, and energy conversion, yet conventional microfluidic systems often require external pumps and complex infrastructure, severely limiting their scalability and adaptability. Directed fluid transport enabled by milli-structured surfaces has rapidly evolved from static, one‑way capillary designs to dynamic, reconfigurable and programmable systems. This transition marks a shift from simple biomimicry toward programmable control of liquid motion, where milli-structures function as the physical hardware and external fields, wettability modulation, or morphological reconfiguration act as software to encode fluidic behavior. In this review, we provide a comprehensive analysis of this paradigm shift by outlining the programming frameworks that govern structural liquid transport, including (i) geometric programming through architected milli-structures, (ii) surface‑chemical programming via adaptive wettability, and (iii) system‑level programming integrating multi‑field stimuli and hierarchical 3D architectures. We critically examine the underlying mechanisms and highlight state‑of‑the‑art platforms spanning unidirectional capillary systems, reconfigurable liquid logic, multi‑phase separation, solar‑thermal evaporation, and contactless field‑driven droplet manipulation. Emerging reconfigurable fluidic systems capable of self‑adjustment, multi‑phase coordination, and energy‑autonomous operation are also discussed. Finally, we outline key challenges—such as durability, scalable manufacturing, multi‑field coupling, and seamless system integration—and propose future opportunities toward autonomous, adaptive, and life‑like fluidic materials as part of an Integrated Bioinspired Intelligent Fluidic Ecosystem (i-BIFE). This review aims to establish a conceptual and technological roadmap for the next generation of programmable and intelligent liquid‑transport milli-structures.